The present invention relates generally to a seat assembly having an adjustable lumbar support and in particular to an improved adjusting mechanism for the lumbar support.
Lumbar supports embodied in the vehicle seat assemblies are well known as illustrated by U.S. Pat. No. 4,725,095. This lumbar support is adjustable and is carried by a bar rotatably mounted to the seat frame for fore and aft movement as the bar is rotated. The adjusted position of the lumbar support member is controlled by a cam rotatably mounted to the seat back frame and engagable with a portion of the lumbar support bar. The cam serves to hold the lumbar support bar in a given position and to rotate the lumbar support bar upon rotation of the cam to adjust the lumbar support.
In order to package the cam and the adjustment mechanism within the seat back, the radius of the cam is limited by the thickness of the seat back. This necessitates the positioning of the cam and its actuating knob in a certain position relative to the lumbar support bar and the lumbar support member. As a result, there is little flexibility in the placement of the actuating knob used to turn the cam. The lumbar support member is naturally positioned adjacent the lumbar region of a seat occupant. The required position of the handle for packaging and proper operation of the mechanism is not necessarily in the best location for reaching and operating by a seat occupant while seated. Typically the position of the actuating knob is higher along the side of the seat back than
It is an object of the present invention therefore to provide an adjustment mechanism for the lumbar support member that enables the adjustment knob to be placed at a location that is easily reached by a seat occupant.
It is a further object of the invention to provide such a mechanism that continues to use a rotating cam for simplicity.
It is a feature of the present invention that the adjustment mechanism includes a link having a cam follower at one end for engagement with the cam and connected at the other end to the lumbar support bar. With such a mechanism, the cam and adjustment knob can be located where desired and the link made of whatever length is necessary to couple the lumbar support bar to the cam.
It is a further feature of the adjustment mechanism of the present invention that in a preferred embodiment, the cam control surface does not include stopping detents to hold the cam and lumbar support member in position but rather the control surface is smooth. Stop detents are provided elsewhere on the cam and are engagable with a spring biased plunger to hold the cam and the lumbar support member in position. By providing stop detents separate from the control surface, the pressure acting upon the lumbar support member will have a limited effect on the force required on the actuating knob to adjust the lumbar support. As a result, the adjustment mechanism is smoother and more consistent in its operation.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.